Myopias Roger

Schmidt, C. A. & Shattuck, S. O., 2014, The Higher Classification of the Ant Subfamily Ponerinae (Hymenoptera: Formicidae), with a Review of Ponerine Ecology and Behavior, Zootaxa 3817 (1), pp. 1-242 : 111-113

Myopias Roger

Fig. 18

Myopias Roger, 1861: 39 (as genus). Type-species: Myopias amblyops Roger, 1861: 39 ; by monotypy.

Trapeziopelta Mayr, 1862: 715 (as genus in Ponerinae [Poneridae]). Type-species: Ponera maligna Smith, F., 1861: 44 ; by monotypy. Willey & Brown, 1983: 249 ( Trapeziopelta as junior synonym of Myopias ).

Bradyponera Mayr, 1886: 362 (as genus). Type-species: Ponera nitida Smith, F., 1861: 45 (junior primary homonym in Ponera , replaced by Myopias mayri [Donisthorpe, 1932]); by monotypy. Willey & Brown, 1983: 249 ( Bradyponera as junior synonym of Myopias ).

Myopias is a moderately large genus (35 described species) restricted to Southeast Asia and Australia. Relatively little is known about its habits, but at least some are specialist predators of millipedes.

Diagnosis. Workers of Myopias are distinctive and unlikely to be mistaken for any other genus. Diagnostic characters of the genus (in combination) include: linear mandibles, blunt medial clypeal projection (absent in some species), round propodeal spiracles, nodiform petiole, strong gastral constriction, and simple tarsal claws. The clypeal projection and simple tarsal claws separate Myopias from Leptogenys , the morphologically most similar (and phylogenetically closest) genus. Buniapone and Paltothyreus also have blunt medial clypeal projections, but they differ in many other characters and are unlikely to be confused with Myopias .

Synoptic description. Worker. Small to large (TL 2.8–16.9 mm) ants with the standard characters of Ponerini . Mandibles usually narrow and moderately curved (triangular in M. delta ), with only a few teeth, often without a distinct basal angle, and with a strong basal groove. Clypeus very shallow, the frontal lobes reaching or surpassing the anterior clypeal margin, which usually has a small blunt anterior projection. Eyes very small to moderate in size (rarely absent), located far anterior of the head midline. Mesopleuron not divided by a transverse groove (though sometimes with a row of foveae giving the impression of a groove). Metanotal groove shallow to deep. Propodeum broad dorsally. Propodeal spiracles small and round. Metatibial spur formula (1s, 1p). Petiole nodiform, widening posteriorly and dorsally. Gaster with a strong girdling constriction between pre- and postsclerites of A4. Presence of stridulitrum on pretergite of A4 variable. Head and body foveolate or smooth and shining, sometimes with lateral striations on the mesosoma. Head and body with scattered pilosity and little to no pubescence. Color variable, yellow to black.

Queen. Similar to worker but usually slightly larger (sometimes smaller, as in M. chapmani ), alate and with the other caste differences typical for ponerines ( Willey & Brown, 1983). Ergatoid queens occur in at least some species.

Male. Undescribed and apparently unknown.

Larva. Larvae of some Myopias species have been described by Wheeler & Wheeler (1964, 1976).

Geographic distribution. The range of Myopias extends from Sri Lanka in the west and China in the north to Australia and Tasmania, with the greatest species diversity in Indonesia and New Guinea ( Willey & Brown, 1983).

Ecology and behavior. Myopias is a poorly known genus, probably due to its cryptic nesting and foraging habits. Most of what is known about its ecology and behavior comes from anecdotal observations. Nests are generally constructed in rotting wood, though some species are subterranean nesters ( Wheeler, 1923b; Willey & Brown, 1983). Reported colony sizes are typically less than 100 workers, and often much less ( Wilson, 1959a; Willey & Brown, 1983; Gobin et al, 2006). At least some species are polygynous, and ergatoid queens (in conjunction with normal dealate queens) occur in at least two species ( M. concava and an undescribed Indonesian species; Willey & Brown, 1983; Gobin et al., 2006). Workers of M. emeryi are obligately sterile ( Gobin et al., 2006). Males have apparently never been reported for any Myopias species , which could simply be a reflection of the paucity of observations of any kind for this genus, or may suggest an unusual reproductive strategy. The feeding habits of most species are unknown, but some species are specialist predators of millipedes ( Wilson, 1959a; Willey & Brown, 1983) and M. delta is a specialist predator of ants (especially myrmicines but also other ponerines). Gobin et al. (2003b) identified subepithelial glands in M. emeryi and M. maligna which may function in hydrocarbon production. Abdominal glands within a number of Myopias species were examined by Billen et al. (2013), leading to the discovery of several glands which were previously unknown in ants.

Phylogenetic and taxonomic considerations. Myopias was erected by Roger (1861) to house his newly described species M. amblyops . Except for a brief provisional synonymy under Pachycondyla ( Brown, 1973; Snelling, 1981), Myopias has always been treated as a distinct genus. Emery (1911) placed the genus in his subtribe Plectroctenini , based on very weak characters (sculpturing, pubescence, and the presence of a pectinate spur on the meso- and metatibiae). Willey & Brown (1983) synonymized the genus Trapeziopelta and its junior synonym Bradyponera under Myopias .

We continue to treat Myopias as a distinct genus, based on both molecular and morphological data. Schmidt's (2013) molecular phylogeny of Ponerinae places Myopias with strong support in the Odontomachus group, probably as sister to Leptogenys , though sister relationships to Mesoponera (s.s.) or Leptogenys + Mesoponera cannot be rejected.

Emery (1911) separated Myopias and Trapeziopelta based on characters of the clypeus (in Trapeziopelta the clypeus has a medial blunt anterior projection, which is lacking in Myopias s.s.) and mandibular teeth. Myopias (s.s.) was restricted to a few small hypogeic species, while Trapeziopelta was considered to include most of the taxa now included in Myopias . Though Schmidt (2013) did not have molecular data for any species of Myopias s.s., we tentatively agree with the synonymy of these genera by Willey & Brown (1983). It seems likely that either Trapeziopelta represents a distinct clade within Myopias (with the clypeal projection being an apomorphy of this group), or that the presence of the clypeal projection is plesiomorphic and was subsequently lost in a handful of species which evolved more cryptic habits (perhaps several times independently). It will be necessary to obtain molecular data for M. amblyops or another member of Myopias (s.s.) in order to test these hypotheses. It is also possible that Myopias and Trapeziopelta will prove to be unrelated lineages, though we do not think this is likely.

Figures

FIGURE 18. Worker caste of Myopias chapmani: lateral and dorsal view of body and full-face view of head (CASENT0172093, April Nobile and www.antweb.org); world distribution of Myopias.